1. FIELD OF THE INVENTION
The present invention relates to a process of forming color photographic images having improved color reproduction, and in particular, the invention relates to a process of forming color photographic images having improved color reproduction for multilayer color photographic materials containing, as at least a color coupler, an acylacetamide compound of which one active hydrogen at the alpha-position has been substituted by a releasable group at coupling.
2. DESCRIPTION OF THE PRIOR ART
A multilayer color photographic material usually comprises a silver halide photosensitive emulsion layer containing a yellow coupler and which is sensitive mainly to blue light (light of a wavelength of substantially shorter than about 500 nm), a silver halide photosensitive emulsion layer containing a magenta coupler and which is sensitive mainly to green light (light of a wavelength of substantially about 500 to 600 nm), and a silver halide photosensitive emulsion layer containing a cyan coupler and which is sensitive mainly to red light (light of a wavelength longer than about 590 nm). Each of the photosensitive emulsion layers must function independently for color reproduction. To obtain this result, intermediate layers, a filter layer to light including ultraviolet light, an antihalation layer, and a protective layer are formed in the color photographic material in addition to the above-described silver halide photosensitive emulsion layers.
Furthermore, each silver halide photosensitive emulsion layer must contain a coupler which provides a dye image having an appropriate spectral sensitivity distribution and an appropriate spectral absorption in a specific wavelength region. However, present color photographic materials still have many defects as shown below.
The first defect in color reproduction is in the spectral absorption characteristics of the colored dye image formed from the coupler, in that the dye image does not have sufficient absorption in a specific wavelength region and has unnecessary absorption in other wavelength regions. Such a defect narrows the color reproduction region and also causes a shift in the hue and a reduction in saturation. The second defect is that the development of a specific silver halide photosensitive emulsion layer induces the coloring of couplers in adjacent silver halide emulsion layers. This disadvantage causes color mixing and reduces, in particular, saturation. The third defect is that a sensitizing dye used for spectrally sensitizing a specific silver halide emulsion layer diffuses into an adjacent silver halide emulsion layer to sensitize the adjacent layer, whereby the silver halide emulsion layer has an inappropriate spectral sensitivity distribution.
As a method of improving these defects, a method of forming intermediate layers and a filter layer and also a method wherein a reducing agent such as a hydroquinone derivative, a phenol derivative, an ascorbic acid derivative, a scavenger for the oxidation product of a color developing agent which is an aromatic primary compound, a colorless coupler, a coupler forming a diffusible dye, and a sensitizing dye or a diffusion preventing agent for a coupler such as fine silver halide grains, a clay such as colloidal silica and hectorite, an anionic surface active agent, a nonionic surface active agent, a cationic surface active agent, a cationic hydrophilic synthetic polymer, a hydroquinone derivative-containing hydrophilic polymer, and a polymer latex incorporated in an intermediate layer or a filter layer, are known. However, the improvement with such methods is still insufficient.
Another method of improving the occurence of "color mixing" is the introduction of a photographic element positively equipped with a "color correction" function. The first attempt of this nature is a method of using a colored coupler equipped with an automatic masking funtion as described in, for instance, the specifications of U.S. Pat. Nos. 2,455,170; 2,449,966; 2,600,788; 2,428,054; 3,148,062; and 2,983,608 and British Pat. No. 1,044,778. However, the use of the colored coupler tends to increase the formation of fog, which degrades the granularity of the dye image formed, and hence the use of such a coupler is generally limited.
The second attempt is a method of using a so-called "DIR coupler (development inhibitor releasing coupler)". A DIR coupler is a coupler defined in D. R. Barr, J. R. Thirtle, and P. W. Vittum, Photographic Science and Eng., Vol. 13, 74 .about. 80 (1969); ibid., 214 - 217 (1969); and U.S. Pat. No. 3,227,554. It is generally known that the DIR coupler provides an interimage effect but has the disadvantages that it delays the development, reduces the gradation (gamma), reduces the maximum color density (Dmax), and reduces the effective sensitivity.
The third attempt is a method of using a substantially fogged silver halide emulsion as an intermediate layer. This method, however, generally provides a low effect in improving the color reproduction and, in particular, when the amount of silver halide is reduced in at least one silver halide photosensitive emulsion layer using therein a color coupler having a high coupling ability, the method tends to provide substantially no effect in improving color reproduction. Furthermore, an ordinary multilayer color photographic material has, from the support side, a red-sensitive silver halide emulsion layer, a green-sensitive silver halide emulsion layer, and a blue-sensitive silver halide emulsion layer on a support and in such a case the sharpness of the green-sensitive silver halide emulsion layer and the red-sensitive silver halide emulsion layer disposed under the blue-sensitive silver halide emulsion layer is reduced due to light scattering by the the silver halide grains in the blue-sensitive silver halide emulsion layer (in this proposed attempt). The reduction in sharpness can be, however, improved because, as will be explained hereinafter in detail, when an acylacetamide compound in which at least one active hydrogen at the alpha-position having a high coupling ability has been substituted by a releasable group at coupling is used as a coupler in place of an acylacetamide compound in which the alpha-position has not been substituted, the amount of the silver halide incorporated in the blue-sensitive silver halide emulsion layer can be generally reduced to about a half that generally required. By employing the aforesaid technique, the sharpness of the green-sensitive halide emulsion layer and the red-sensitive silver halide emulsion layer can be remarkably increased, but as described above the aforesaid third attempt tends to provide almost no effect in improving color reproduction. As described above, if improving the sharpness of the silver halide emulsion layers using a fogged silver halide emulsion in the intermediate layers is intended, the effect of improving color reproduction becomes poor and thus it has been difficult to obtain high sharpness and good color reproduction simultaneously using the third attempt as proposed heretofore.